Irreversible electroporation (IRE) is a new tissue ablation technique in which very high energy electrical pulses are delivered to undesirable tissue to produce cell necrosis. Currently the only commercially available single probe bipolar device for an irreversible electroporation (IRE) procedure is capable of creating a maximum of 1.5 cm ablation. In cases where there is a need for a larger ablation, the user/physician needs to use two or more single probes to perform the ablation. Generally, the size of ablation/tumor will determine the number of probes (at times up to six) that are needed to be used to perform the procedure. These probes need to be closely aligned and tightly spaced to achieve optimal IRE ablation results. The need to place several probes and have them closely aligned can potentially complicate and lengthen the procedure time and consequently the operating room use time required.
Various configurations of antennae as well as electrode probes for ablation of undesired tissue in a patient are known in the art. The term “antennae” and “tines” are known in the art as referring to aspects of radiofrequency (RF) devices and the term “electrode” is known in the art as referring to electrical devices in the context of supraporation (electropurturbation) devices, electroporation (RE) devices and especially in irreversible electroporation (IRE) devices. For convenience and efficiency, in this application, the terms “antennae”, “tine” and “electrode” are used interchangeably whether in single or plural form to refer to parts that deliver electrical energy in electrical ablation devices including RF, supraporation, RE and IRE devices.
A detailed explanation of IRE can be found, for example, in U.S. Patent Application Publication No. 2006/0293731, entitled “Methods and systems for treating tumors using electroporation”, application Ser. No. 11/165,961 filed on Jun. 24, 2005, which is hereby incorporated by reference. In IRE, electrical pulses in the range of microseconds to milliseconds can be applied to a target tissue zone to produce defects in the cell membrane that are nanoscale in size. The defects in the cell membrane lead to a disruption of homeostasis and eventually cause the cells to die. IRE devices can be designed to be non-thermal and the IRE pulses do not destroy connective and scaffolding structure in the target zone such as nerves and blood vessels.
The IRE pulses are applied using electrical probes, which can be monopolar, bipolar or multi-electrode. The probe designs are similar to the RF probes and accordingly are subject to some of the same problems involving energy distribution along the electrodes.
A single bipolar probe or multi-electrode probe can be used to ablate diseased or unwanted tissue. The positive and negative electrodes are located on a single probe and the tissue is ablated as energy flows from the positive to the negative electrode. Although the bipolar design provides efficient energy deposition in the tissue, the maximum ablation volume is limited and the resulting cylindrical shape of ablation often does not correspond with the targeted tumor shape.
Probes having electrode arrays with an umbrella-like profile achieve larger, more spherical ablations with a single puncture. In this type of probe, two or more outwardly curving tines (electrodes) are placed within the tumor, at predetermined positions, and electrical energy flows between one or more pairs of active tines or electrodes in the array. However, while the array of electrodes in this type of probe is being deployed, the electrodes may lack sufficient strength to adequately pierce through the tissue or may deploy at a wrong angle and can therefore deviate from their intended trajectory. For example, the electrodes may lack sufficient strength to pierce through certain types of more rigid “soft” tissues, such as such as tissues found in the liver, kidneys, lungs, etc. If the electrodes deviate from their intended path and are not ultimately positioned in their predetermined intended locations, treatment of the tissue may not be successful and/or other risks and dangers to the patient may be presented.